Abstract
Many (K~1−x~Na~x~)NbO~3~ (KNN)‐based ceramics with high piezoelectric performance exhibit undesirable strong temperature dependence due to the orthorhombic–tetragonal polymorphic phase transition near room temperature. In order to improve the temperature stability of the ceramics, many additives have been added into the KNN‐based ceramics to shift T~O–T~ down to below room temperature. Contrary to the previous approach (Na~0.53~K~0.47−x~Ag~x~)Nb~1−x~Sb~x~O~3~ (NKANS) ceramics with T~O–T~ well above room temperature have been prepared by a conventional solid‐state reaction method. The density and the electrical properties are effectively improved by the addition of AgSbO~3~, and optimum piezoelectric properties are found in the ceramics with 0.05 ≤ x ≤ 0.07, with maximum k~p~ ∼ 0.46 for NKANS5 and maximum d~33~ ∼ 199 pC/N for NKANS7. More importantly, k~p~ remains virtually almost unchanged up to the T~O–T~ temperature (≥100 °C), indicating that the NKANS ceramics exhibit a much improved piezoelectric thermal stability. The analyses suggest that both the high T~O–T~ value and diffuse orthorhombic–tetragonal phase transition should be responsible for the good temperature stability.